The present invention relates to a new process for the manufacture of 1-amino-1-methyl-3(4)-cyanocyclohexane (AMCC), which can be converted by hydrogenation to 1-amino-1-methyl-3(4)-amino-methyl-cyclohexane (AMCA), the intermediate for the manufacture of 1-isocyanato-1-methyl-3(4)-isocyanatomethyl-cyclohexane (IMCI).
EP-A 0 153 561 discloses that IMCI is a diisocyanate of high quality that has a variety of uses in polyurethane chemistry. IMCI may be obtained by the following schematic synthesis sequence: ##STR1##
A key step in the course of this reaction scheme is the Ritter reaction (3). This reaction makes it possible to introduce an amino group bonded to a tertiary carbon atom. The Ritter reaction is preferably carried out in sulfuric acid because the corresponding formamide is primarily formed from the olefinic intermediate and hydrogen cyanide and subsequently hydrolyzed. The salt of AMCA, which is present in solution in the reaction mixture, is formed in this way. As is customary in the workup of Ritter reaction mixtures, the diamine is subsequently liberated with alkaline materials (e.g. caustic soda solution) and isolated by extraction with suitable solvents from the aqueous solution of the alkali metal salts.
In the course of the synthesis in accordance with the above-illustrated scheme, a large amount of unusable waste salts is formed. This waste makes large-scale production by this process prohibitive due to the environmental pollution generated. A stoichiometric consideration of Examples (1a) and (1b) of EP-A-0 153 561 shows that in the best case more than 4 t of a waste mixture of sodium sulfate and formate is formed. In the least favorable case, nearly 9 t of this waste are generated per metric ton of AMCA.